lisp/gnus/shr-color.el

   1 ;;; shr-color.el --- Simple HTML Renderer color management
   2
   3 ;; Copyright (C) 2010-2011 Free Software Foundation, Inc.
   4
   5 ;; Author: Julien Danjou <julien@danjou.info>
   6 ;; Keywords: html
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24
  25 ;; This package handles colors display for shr.
  26
  27 ;;; Code:
  28
  29 (require 'color)
  30 (eval-when-compile (require 'cl))
  31
  32 (defgroup shr-color nil
  33   "Simple HTML Renderer colors"
  34   :group 'shr)
  35
  36 (defcustom shr-color-visible-luminance-min 40
  37   "Minimum luminance distance between two colors to be considered visible.
  38 Must be between 0 and 100."
  39   :group 'shr
  40   :type 'float)
  41
  42 (defcustom shr-color-visible-distance-min 5
  43   "Minimum color distance between two colors to be considered visible.
  44 This value is used to compare result for `ciede2000'. Its an
  45 absolute value without any unit."
  46   :group 'shr
  47   :type 'integer)
  48
  49 (defconst shr-color-html-colors-alist
  50   '(("AliceBlue" . "#F0F8FF")
  51     ("AntiqueWhite" . "#FAEBD7")
  52     ("Aqua" . "#00FFFF")
  53     ("Aquamarine" . "#7FFFD4")
  54     ("Azure" . "#F0FFFF")
  55     ("Beige" . "#F5F5DC")
  56     ("Bisque" . "#FFE4C4")
  57     ("Black" . "#000000")
  58     ("BlanchedAlmond" . "#FFEBCD")
  59     ("Blue" . "#0000FF")
  60     ("BlueViolet" . "#8A2BE2")
  61     ("Brown" . "#A52A2A")
  62     ("BurlyWood" . "#DEB887")
  63     ("CadetBlue" . "#5F9EA0")
  64     ("Chartreuse" . "#7FFF00")
  65     ("Chocolate" . "#D2691E")
  66     ("Coral" . "#FF7F50")
  67     ("CornflowerBlue" . "#6495ED")
  68     ("Cornsilk" . "#FFF8DC")
  69     ("Crimson" . "#DC143C")
  70     ("Cyan" . "#00FFFF")
  71     ("DarkBlue" . "#00008B")
  72     ("DarkCyan" . "#008B8B")
  73     ("DarkGoldenRod" . "#B8860B")
  74     ("DarkGray" . "#A9A9A9")
  75     ("DarkGrey" . "#A9A9A9")
  76     ("DarkGreen" . "#006400")
  77     ("DarkKhaki" . "#BDB76B")
  78     ("DarkMagenta" . "#8B008B")
  79     ("DarkOliveGreen" . "#556B2F")
  80     ("Darkorange" . "#FF8C00")
  81     ("DarkOrchid" . "#9932CC")
  82     ("DarkRed" . "#8B0000")
  83     ("DarkSalmon" . "#E9967A")
  84     ("DarkSeaGreen" . "#8FBC8F")
  85     ("DarkSlateBlue" . "#483D8B")
  86     ("DarkSlateGray" . "#2F4F4F")
  87     ("DarkSlateGrey" . "#2F4F4F")
  88     ("DarkTurquoise" . "#00CED1")
  89     ("DarkViolet" . "#9400D3")
  90     ("DeepPink" . "#FF1493")
  91     ("DeepSkyBlue" . "#00BFFF")
  92     ("DimGray" . "#696969")
  93     ("DimGrey" . "#696969")
  94     ("DodgerBlue" . "#1E90FF")
  95     ("FireBrick" . "#B22222")
  96     ("FloralWhite" . "#FFFAF0")
  97     ("ForestGreen" . "#228B22")
  98     ("Fuchsia" . "#FF00FF")
  99     ("Gainsboro" . "#DCDCDC")
 100     ("GhostWhite" . "#F8F8FF")
 101     ("Gold" . "#FFD700")
 102     ("GoldenRod" . "#DAA520")
 103     ("Gray" . "#808080")
 104     ("Grey" . "#808080")
 105     ("Green" . "#008000")
 106     ("GreenYellow" . "#ADFF2F")
 107     ("HoneyDew" . "#F0FFF0")
 108     ("HotPink" . "#FF69B4")
 109     ("IndianRed" . "#CD5C5C")
 110     ("Indigo" . "#4B0082")
 111     ("Ivory" . "#FFFFF0")
 112     ("Khaki" . "#F0E68C")
 113     ("Lavender" . "#E6E6FA")
 114     ("LavenderBlush" . "#FFF0F5")
 115     ("LawnGreen" . "#7CFC00")
 116     ("LemonChiffon" . "#FFFACD")
 117     ("LightBlue" . "#ADD8E6")
 118     ("LightCoral" . "#F08080")
 119     ("LightCyan" . "#E0FFFF")
 120     ("LightGoldenRodYellow" . "#FAFAD2")
 121     ("LightGray" . "#D3D3D3")
 122     ("LightGrey" . "#D3D3D3")
 123     ("LightGreen" . "#90EE90")
 124     ("LightPink" . "#FFB6C1")
 125     ("LightSalmon" . "#FFA07A")
 126     ("LightSeaGreen" . "#20B2AA")
 127     ("LightSkyBlue" . "#87CEFA")
 128     ("LightSlateGray" . "#778899")
 129     ("LightSlateGrey" . "#778899")
 130     ("LightSteelBlue" . "#B0C4DE")
 131     ("LightYellow" . "#FFFFE0")
 132     ("Lime" . "#00FF00")
 133     ("LimeGreen" . "#32CD32")
 134     ("Linen" . "#FAF0E6")
 135     ("Magenta" . "#FF00FF")
 136     ("Maroon" . "#800000")
 137     ("MediumAquaMarine" . "#66CDAA")
 138     ("MediumBlue" . "#0000CD")
 139     ("MediumOrchid" . "#BA55D3")
 140     ("MediumPurple" . "#9370D8")
 141     ("MediumSeaGreen" . "#3CB371")
 142     ("MediumSlateBlue" . "#7B68EE")
 143     ("MediumSpringGreen" . "#00FA9A")
 144     ("MediumTurquoise" . "#48D1CC")
 145     ("MediumVioletRed" . "#C71585")
 146     ("MidnightBlue" . "#191970")
 147     ("MintCream" . "#F5FFFA")
 148     ("MistyRose" . "#FFE4E1")
 149     ("Moccasin" . "#FFE4B5")
 150     ("NavajoWhite" . "#FFDEAD")
 151     ("Navy" . "#000080")
 152     ("OldLace" . "#FDF5E6")
 153     ("Olive" . "#808000")
 154     ("OliveDrab" . "#6B8E23")
 155     ("Orange" . "#FFA500")
 156     ("OrangeRed" . "#FF4500")
 157     ("Orchid" . "#DA70D6")
 158     ("PaleGoldenRod" . "#EEE8AA")
 159     ("PaleGreen" . "#98FB98")
 160     ("PaleTurquoise" . "#AFEEEE")
 161     ("PaleVioletRed" . "#D87093")
 162     ("PapayaWhip" . "#FFEFD5")
 163     ("PeachPuff" . "#FFDAB9")
 164     ("Peru" . "#CD853F")
 165     ("Pink" . "#FFC0CB")
 166     ("Plum" . "#DDA0DD")
 167     ("PowderBlue" . "#B0E0E6")
 168     ("Purple" . "#800080")
 169     ("Red" . "#FF0000")
 170     ("RosyBrown" . "#BC8F8F")
 171     ("RoyalBlue" . "#4169E1")
 172     ("SaddleBrown" . "#8B4513")
 173     ("Salmon" . "#FA8072")
 174     ("SandyBrown" . "#F4A460")
 175     ("SeaGreen" . "#2E8B57")
 176     ("SeaShell" . "#FFF5EE")
 177     ("Sienna" . "#A0522D")
 178     ("Silver" . "#C0C0C0")
 179     ("SkyBlue" . "#87CEEB")
 180     ("SlateBlue" . "#6A5ACD")
 181     ("SlateGray" . "#708090")
 182     ("SlateGrey" . "#708090")
 183     ("Snow" . "#FFFAFA")
 184     ("SpringGreen" . "#00FF7F")
 185     ("SteelBlue" . "#4682B4")
 186     ("Tan" . "#D2B48C")
 187     ("Teal" . "#008080")
 188     ("Thistle" . "#D8BFD8")
 189     ("Tomato" . "#FF6347")
 190     ("Turquoise" . "#40E0D0")
 191     ("Violet" . "#EE82EE")
 192     ("Wheat" . "#F5DEB3")
 193     ("White" . "#FFFFFF")
 194     ("WhiteSmoke" . "#F5F5F5")
 195     ("Yellow" . "#FFFF00")
 196     ("YellowGreen" . "#9ACD32"))
 197   "Alist of HTML colors.
 198 Each entry should have the form (COLOR-NAME . HEXADECIMAL-COLOR).")
 199
 200 (defun shr-color-relative-to-absolute (number)
 201   "Convert a relative NUMBER to absolute. If NUMBER is absolute, return NUMBER.
 202 This will convert \"80 %\" to 204, \"100 %\" to 255 but \"123\" to \"123\"."
 203   (let ((string-length (- (length number) 1)))
 204     ;; Is this a number with %?
 205     (if (eq (elt number string-length) ?%)
 206         (/ (* (string-to-number (substring number 0 string-length)) 255) 100)
 207       (string-to-number number))))
 208
 209 (defun shr-color-hue-to-rgb (x y h)
 210   "Convert X Y H to RGB value."
 211   (when (< h 0) (incf h))
 212   (when (> h 1) (decf h))
 213   (cond ((< h (/ 1 6.0)) (+ x (* (- y x) h 6)))
 214         ((< h 0.5) y)
 215         ((< h (/ 2.0 3.0)) (+ x (* (- y x) (- (/ 2.0 3.0) h) 6)))
 216         (t x)))
 217
 218 (defun shr-color-hsl-to-rgb-fractions (h s l)
 219   "Convert H S L to fractional RGB values."
 220   (let (m1 m2)
 221     (if (<= l 0.5)
 222         (setq m2 (* l (+ s 1)))
 223         (setq m2 (- (+ l s) (* l s))))
 224     (setq m1 (- (* l 2) m2))
 225     (list (shr-color-hue-to-rgb m1 m2 (+ h (/ 1 3.0)))
 226           (shr-color-hue-to-rgb m1 m2 h)
 227           (shr-color-hue-to-rgb m1 m2 (- h (/ 1 3.0))))))
 228
 229 (defun shr-color->hexadecimal (color)
 230   "Convert any color format to hexadecimal representation.
 231 Like rgb() or hsl()."
 232   (when color
 233     (cond
 234      ;; Hexadecimal color: #abc or #aabbcc
 235      ((string-match
 236        "\\(#[0-9a-fA-F]\\{3\\}[0-9a-fA-F]\\{3\\}?\\)"
 237        color)
 238       (match-string 1 color))
 239      ;; rgb() or rgba() colors
 240      ((or (string-match
 241            "rgb(\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*)"
 242            color)
 243           (string-match
 244            "rgba(\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*\\([0-9]\\{1,3\\}\\(?:\s*%\\)?\\)\s*,\s*[0-9]*\.?[0-9]+\s*%?\s*)"
 245            color))
 246       (format "#%02X%02X%02X"
 247               (shr-color-relative-to-absolute (match-string-no-properties 1 color))
 248               (shr-color-relative-to-absolute (match-string-no-properties 2 color))
 249               (shr-color-relative-to-absolute (match-string-no-properties 3 color))))
 250      ;; hsl() or hsla() colors
 251      ((or (string-match
 252            "hsl(\s*\\([0-9]\\{1,3\\}\\)\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*)"
 253            color)
 254           (string-match
 255            "hsla(\s*\\([0-9]\\{1,3\\}\\)\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*,\s*\\([0-9]\\{1,3\\}\\)\s*%\s*,\s*[0-9]*\.?[0-9]+\s*%?\s*)"
 256            color))
 257       (let ((h (/ (string-to-number (match-string-no-properties 1 color)) 360.0))
 258             (s (/ (string-to-number (match-string-no-properties 2 color)) 100.0))
 259             (l (/ (string-to-number (match-string-no-properties 3 color)) 100.0)))
 260         (destructuring-bind (r g b)
 261             (shr-color-hsl-to-rgb-fractions h s l)
 262           (color-rgb-to-hex r g b))))
 263      ;; Color names
 264      ((cdr (assoc-string color shr-color-html-colors-alist t)))
 265      ;; Unrecognized color :(
 266      (t
 267       nil))))
 268
 269 (defun set-minimum-interval (val1 val2 min max interval &optional fixed)
 270   "Set minimum interval between VAL1 and VAL2 to INTERVAL.
 271 The values are bound by MIN and MAX.
 272 If FIXED is t, then val1 will not be touched."
 273   (let ((diff (abs (- val1 val2))))
 274     (unless (>= diff interval)
 275       (if fixed
 276           (let* ((missing (- interval diff))
 277                  ;; If val2 > val1, try to increase val2
 278                  ;; That's the "good direction"
 279                  (val2-good-direction
 280                   (if (> val2 val1)
 281                       (min max (+ val2 missing))
 282                     (max min (- val2 missing))))
 283                  (diff-val2-good-direction-val1 (abs (- val2-good-direction val1))))
 284             (if (>= diff-val2-good-direction-val1 interval)
 285                 (setq val2 val2-good-direction)
 286               ;; Good-direction is not so good, compute bad-direction
 287               (let* ((val2-bad-direction
 288                       (if (> val2 val1)
 289                           (max min (- val1 interval))
 290                         (min max (+ val1 interval))))
 291                      (diff-val2-bad-direction-val1 (abs (- val2-bad-direction val1))))
 292                 (if (>= diff-val2-bad-direction-val1 interval)
 293                     (setq val2 val2-bad-direction)
 294                   ;; Still not good, pick the best and prefer good direction
 295                   (setq val2
 296                         (if (>= diff-val2-good-direction-val1 diff-val2-bad-direction-val1)
 297                             val2-good-direction
 298                           val2-bad-direction))))))
 299         ;; No fixed, move val1 and val2
 300         (let ((missing (/ (- interval diff) 2.0)))
 301           (if (< val1 val2)
 302               (setq val1 (max min (- val1 missing))
 303                     val2 (min max (+ val2 missing)))
 304             (setq val2 (max min (- val2 missing))
 305                   val1 (min max (+ val1 missing))))
 306           (setq diff (abs (- val1 val2)))   ; Recompute diff
 307           (unless (>= diff interval)
 308             ;; Not ok, we hit a boundary
 309             (let ((missing (- interval diff)))
 310               (cond ((= val1 min)
 311                      (setq val2 (+ val2 missing)))
 312                     ((= val2 min)
 313                      (setq val1 (+ val1 missing)))
 314                     ((= val1 max)
 315                      (setq val2 (- val2 missing)))
 316                     ((= val2 max)
 317                      (setq val1 (- val1 missing)))))))))
 318     (list val1 val2)))
 319
 320 (defun shr-color-visible (bg fg &optional fixed-background)
 321   "Check that BG and FG colors are visible if they are drawn on each other.
 322 Return (bg fg) if they are. If they are too similar, two new
 323 colors are returned instead.
 324 If FIXED-BACKGROUND is set, and if the color are not visible, a
 325 new background color will not be computed. Only the foreground
 326 color will be adapted to be visible on BG."
 327   ;; Convert fg and bg to CIE Lab
 328   (let ((fg-norm (color-name-to-rgb fg))
 329         (bg-norm (color-name-to-rgb bg)))
 330     (if (or (null fg-norm)
 331             (null bg-norm))
 332         (list bg fg)
 333       (let* ((fg-lab (apply 'color-srgb-to-lab fg-norm))
 334              (bg-lab (apply 'color-srgb-to-lab bg-norm))
 335              ;; Compute color distance using CIE DE 2000
 336              (fg-bg-distance (color-cie-de2000 fg-lab bg-lab))
 337              ;; Compute luminance distance (substract L component)
 338              (luminance-distance (abs (- (car fg-lab) (car bg-lab)))))
 339         (if (and (>= fg-bg-distance shr-color-visible-distance-min)
 340                  (>= luminance-distance shr-color-visible-luminance-min))
 341             (list bg fg)
 342           ;; Not visible, try to change luminance to make them visible
 343           (let ((Ls (set-minimum-interval (car bg-lab) (car fg-lab) 0 100
 344                                           shr-color-visible-luminance-min
 345                                           fixed-background)))
 346             (unless fixed-background
 347               (setcar bg-lab (car Ls)))
 348             (setcar fg-lab (cadr Ls))
 349             (list
 350              (if fixed-background
 351                  bg
 352                (apply 'format "#%02x%02x%02x"
 353                       (mapcar (lambda (x) (* (max (min 1 x) 0) 255))
 354                               (apply 'color-lab-to-srgb bg-lab))))
 355              (apply 'format "#%02x%02x%02x"
 356                     (mapcar (lambda (x) (* (max (min 1 x) 0) 255))
 357                             (apply 'color-lab-to-srgb fg-lab))))))))))
 358
 359 (provide 'shr-color)
 360
 361 ;;; shr-color.el ends here